Carbon nanotube supported Ga@PdAgCo anode catalysts for hydrazine electrooxidation in alkaline media

Abstract

In this study, carbon nanotube supported (CNT) monometallic (Pd), trimetallic (PdAgCo), and multimetallic (Ga@PdAgCo) catalysts in different weight percentages (0.5–10%) are synthesized by the NaBH4 reduction method and characterized transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray diffraction (XRD) analytical methods. According to the TEM analysis results, while agglomeration doesn’t observe for 3% Ga@PdAgCo(80:10:10)/CNT catalyst, agglomeration is observed in certain parts for 7% Ga@PdAgCo(80:10:10)/CNT catalyst. The occurrence of agglomeration has a negative effect on catalytic activity. XRD analysis shows that as metal was added, the diffraction peaks are negatively shifted, thereby forming an alloy. Electrochemical measurements such as cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) are used for the hydrazine electrooxidation activities of the catalysts. The highest specific activity is achieved as 250.39 mA/cm2 (22592.66 mA/mg Pd) with catalyst. The electrochemical surface area (ECSA) of 3% Ga@PdAgCo/CNT catalysts is also calculated as 1392.43 m2/g. The homogeneous distribution of the metals on the support material and the alloy formation has an effect on the catalytic activity for the 3% Ga@PdAgCo(80:10:10)/CNT catalyst. Although Pd is an active metal on its own, the synergistic effect between them as a result of the formation of alloys with different metals and the electronic state change on the catalyst by adding different metals to Pd has a great influence on the catalytic activity. As a result, Ga@PdAgCo/CNT catalyst with its high current value stands out as a new anode catalyst for hydrazine electrooxidation.